The high cost and dwindling supply of fossil fuels have created intense interest in alternate sources of energy. One such alternate energy source involves the utilization of the temperature difference between warm surface seawater and cooler subsurface seawater. This general concept is known as ocean thermal energy conversion or "OTEC".
In one popular version of an OTEC power plant, warm surface seawater is used to vaporize a working fluid. The vapor is used to drive turbine generators which ultimately produce electricity. After the vapor has passed through the turbines, cool subsurface seawater is used to condense the vapor, thereby completing the working fluid cycle.
The cool subsurface seawater required for this process is located roughly 1500 to 3000 feet below the water surface. In the design of many OTEC power plants, it is necessary to bring large quantities of this subsurface seawater to the surface. To accomplish this, it is envisioned that a long pipe commonly referred to as a "cold water conduit" will be used, said conduit to extend from the surface downward roughly 1500 to 3000 feet. It is anticipated that the conduit must be approximately 5 to 120 feet in diameter for OTEC powerplants from 1 to 400 megawatts, respectively.
The need for such a huge conduit presents several severe problems. The conduit must be fabricated of a material which is strong enough to withstand the tremendous dynamic wave loads as well as the large static load presented by the weight of such a long vertical conduit. Other problems involve the method of installing such a conduit and maintaining its position with respect to the OTEC plant located on the surface.